In recent years, as a battery that meets the expectations for miniaturization, lightness, and high capacity, a non-aqueous electrolyte-based secondary battery such as a lithium ion battery has been suggested, and has been put into practical use.
The lithium ion battery includes positive electrode and negative electrode that have properties capable of reversibly intercalating and deintercalating lithium ions, and a non-aqueous electrolyte.
With regard to a negative electrode material of the lithium ion battery, as a negative electrode-active material, Li-containing metal oxides such as a carbon-based material and lithium titanate (Li4Ti5O12) that have properties capable of reversibly intercalating and deintercalating lithium ions have been used.
On the other hand, as a positive electrode material of the lithium ion battery, an electrode material mixture, which contains a Li-containing metal oxide such as iron lithium phosphate (LiFePO4) having properties capable of reversibly intercalating and deintercalating lithium ions as a positive electrode-active material, a binder, and the like, has been used. In addition, this electrode material mixture is applied on a surface of metal foil called a current collector to form a positive electrode of the lithium ion battery.
Since the lithium ion battery is light in weight and small in size, and has high energy compared to a secondary battery such as a lead battery, a nickel-cadmium battery, a nickel-hydrogen battery, and the like in the related art, the lithium ion battery has been used as a power supply of portable electronic apparatuses such as a cellular phone and a note-type personal computer. In addition, in recent years, the lithium ion battery has been reviewed as a high-output power supply of an electric vehicle, a hybrid vehicle, an electromotive tool, and the like, and high-speed charge and discharge characteristics have been required for the battery that is used as the high-output power supply.
However, the electrode material, which contains an electrode-active material, for example, the Li-containing metal oxide having properties capable of reversibly intercalating and deintercalating lithium ions, has a problem in that conductivity is low. Therefore, there is suggested an electrode material in which a particle surface of the electrode-active material is covered with an organic component that is a carbon source, the organic component are carbonized to form a carbonaceous film on a surface of the electrode-active material, and carbon of the carbonaceous film is interposed as an electronic conductive material to increase the conductivity of the electrode material (refer to PTL 1).